Instead of doing yet another Sunosub project, I've decided to go with the wood box equivalent sub using the original SVS driver. I'm building this for a local friend/member. We've settled on a 18"x18" footprint, looking at 4.5ft^3 to 5ft^3 of internal volume, tuned to 20Hz with a 16"-18" long flared 4" port. The internal height will be around 40", and width/depth will be 16.5"x16.5". Driver will be down-firing, port though the top, a la SVS. Powered by the 250W plate amp on sale from MCM last week. Will have bottom plate as well, with 4"-6" legs separating the driver from the plate. Bracing options are my main concerns. Should I just use horizontal layers (with holes cut into them to accomodate airflow and the port) and not much in terms of bracing in the vertical orientation? Or do I need some vertical bracing as well? Links to other box sub constructions are welcomed, of course. TIA.